Die casting machine



Oct. 21 1958 4 Sheets-Sheet 1 Filed Aug. 2. 1954 m m m m R m m N A m a w1 w 6 m bw fi dfw NM, mfi m fi NM, M mm Om 3 MW WW m N ANIIII Oct.2l,1958 L. RING 2,856,656

I DIE CASTING MACHINE Filed Aug. 2. 1954 4 Sheets-Sheet 2 INVENTOR.Z(/C'/4/V lF/NG BYW L. RING DIE CASTING MACHINE Oct. 21, 1958 Filed Aug.2. 1954 4 Sheets-Sheet 3 INVENTOR.

Arramwars Oct. 21, 1958 L. RING DIE CASTING MACHINE Filed Aug. 2. 1954 4Sheets-Sheet 4 INVENTOR. 406/ A/ PIA/6 BY DIE CASTING MACHINE LucianRing, Detroit, Mich., assignor to Ring Aluminum Development Company, acorporation of Michigan Application August 2, 1954, Serial No. 447,27911 Claims. (Cl. 22-68) This invention relates generally to pressurecasting equipment and refers more particularly to improvements inequipment of the type disclosed in my copending application-Serial No.382,079, filed September 24, 1953, now Patent No. 2,837,792, grantedJune 10, 1958.

In die casting, certain metals such, for example, as aluminum, aluminumalloys and metals having similar characteristics, it has been thepractice to ladle the required amount of molten metal by hand into thepressure chamber of a suitable die casting machine in advance of theplunger and thereafter operate the plunger to inject the molten metalinto the die cavity. Hand ladling of the molten casting material intothe pressure chamber not only consumed considerable time and, hence,reduced the rate of production of a given machine but, in addition,rendered it difficult to produce uniform castings due to castingmaterial supplied to the pressure chamber.

In my above identified copending application, the molten castingmaterial is drawn into the pressure chamber by vacuum produced withinthe pressure chamber in response to return movement of the plunger andthis material is subsequently injected into the die cavity of themachine by the plunger as the latter is moved on its pressure strokewithin the pressure chamber. This arrangement eliminates the handladling operation heretofore considered necessary and renders themachine completely automati so that the rate of production of themachine is not only substantially increased but, in addition, moreuniform castings are obtained.

In die casting apparatus of the type set forth in the precedingparagraph, the quantity of molten material admitted to the pressurechamber um produced in the pressure chamber is metered through a supplypassage and does not substantially exceed the amount required to fillthe die cavity and associated gate. This is accomplished by providingthe supply or metering passage with an effective cross sectional areapredetermined with respect to the volume of the cavity and the vacuumproduced in the pressure chamber. The predetermined cross sectional areaof the supply passage must be maintained over long periods of useregardless of the temperature of the molten casting material and regardless of any characteristic this material may possess which tend tocorrode or otherwise deteriorate the walls of the supply passage. Forexample, aluminum and alloys of aluminum have a chemical as well as aphysical action on the walls of the supply passage and continued flow ofthis material through the supply passage has a tendency to increase thesize of the latter to such an extent that the amount of molten castingmaterial admitted to the pressure chamber greatly exceeds therequirements.

With the above in View, it is an object of this invention to provide adie casting machine wherein the predetermined cross sectional area ofthe supply passage is maintained over long periods of use regardless ofthe temperature of the molten material and regardless of the variationsin temperature of the molten by the action of the vacu- The slide 27 ismounted on chemical or physical action of the material on the walls ofthe supply passage.

It is another object of this invention to provide a supply unit whereinthe supply passage for metering the flow of molten casting material intothe pressure chamber is formed in a removable tip composed of a sinteredThe foregoing as well as other objects will be made more apparent asthis description proceeds especially when considered in connection withthe accompanying drawings, wherein Figure l is a side elevational viewpartly in section of die casting apparatus constructed in accordancewith this invention;

Figure 2 is a cross sectional view taken on the line 2-2 of Figure 1;

Figure 3 i a cross sectional view taken on the line 3-3 of Figure 1;

Figure 4 is a sectional view line 4-4 of Figure 3; j i

Figure 5 is a cross sectional view taken on the line 5--5 of Figure 4;

Figure 6 is a sectional view taken on the line 66 of Figure 2;

Figure 7 is a cross sectional view taken on the line 7-7 of Figure 6;

Figure 8 is a cross sectional view taken on the line 88 of Figure 6;

Figure 9 is a cross sectional view taken on the line 99 of Figure 1;

Figure 10 is a sectional'view taken on the line 1010 of Figure 5;

Figure 11 is an enlarged sectional view taken on the line 11-11 ofFigure 1;

Figure 12 is a flow diagram of a part of the apparatus;

Figure 13 is a sectional view taken on the line 13 13 of Figure 11;

Figure 14 is a semi-diagrammatic elevational view of a part of theapparatus shown in Figure 1;

Figure 15 is a sectional view taken on the line 1515 of Figure 4; and

Figure 16 is an enlarged sectional view of a part of the feeding meansfor molten casting material.

In Figure l of the drawing, the numeral 20 designates a typical diestructure having a stationary part 21 and a movable part 22. The part 21is suitably fixed to a frame. member 23 and the part 22 is supported atthe outer side of the part 21 for movement toward and away from thelatter part. The adjacent surfaces of the die parts are fashioned toform a cavity 24 in the closed position of the die and to provide apassage or gate 25 leading into the cavity 24.

The part 22 is secured to housing 26 having the outer takensubstantially on the the inner end of an annular end mounted on a slide27. guide bars 28 having their inner ends secured to the frame member23. Any suitable means not shown herein may be used for moving the slide27 in opposite guides 28 to open and close the die 20.

Mounted within the housing 26 is an ejector plate 29 having pins 30extending inwardly from the plate 29 through bores formed in the diepart 22 and registering with the die cavity 24. The plate 29 is actuatedto eject the casting from the die cavity by a rack bar 31 and pinion 32.The bar 31 is secured to the plate 29 at the outer side of the latterand meshes with the pinion 32 which is driven by any suitable means notshown herein.

Molten metal is introduced into the die cavity 24 through an injectionor pressure cylinder 33 having an outer end projecting through alignedopenings in the frame member 23 and fixed die part 21, as shown inFigures 1 and 4 of the drawings. The outer end of the cylinder 33 isopen and communicates with the die cavity 24 through the medium of thepassage 25. The open outer end of the cylinder 33 may be closed by acylindrical plug 34 slidably supported within a bore formed in themovable die part 22 and having an annular tapered seat 35 at the innerend engageable with an annular tapered seat 36 surrounding the open endof the cylinder 33. The angle of taper of the seats 35 and 36 ispreferably somewhat different in order to assure a fluid tight sealbetween said seats when in contact.

As shown in Figure 1 of the drawings, the plug 34 is reduced at itsouter end and projects axially through the movable die 22 for connectionto the inner end of a lubricant supply tube 37. The tube 37 projectsoutwardly through an opening in the center of the plate 29 and isslidably supported by a bushing 38. The inner end of the tube 37communicates with fluid passages formed in the plug 34 in a manner tolubricate the walls of the bore formed in the die part 22 and the outerend of the tube is connected in any suitable manner to a source oflubricant supply. In this connection, it is to be noted that the bore inthe movable die part 22 within which the plug 34 is slidably supportedis vented to the atmosphere by a passage 39 formed in the movable diepart 22. The purpose of the passage 39 is to prevent a pressure frombuilding up at the outer side of the plug 34 during outward movement ofthe plug relative to the movable die part 22. In addition, it is to benoted that the outer end of the reduced portion of the plug provides ashoulder 40 which is engageable by the ejector plate 29 as the latter ismoved inwardly to eject a casting from the cavity 24. The arrangement issuch that the plug 34 is moved axially inwardly into sealing engagementwith the open outer end of the cylinder 33 by the ejector plate 29 whenthe latter is operated to eject a casting from the die cavity 24. In anycase the plug 34 closes the outer end of the cylinder 33 when the die isopened and renders it possible to produce a vacuum within the cylinder33, as will be presently described.

The inner end of the cylinder 33 is supported in a block 41 which isshown in Figure 3 of the drawings as formed with a vertically elongatedopening 42 therethrough for receiving the cylinder 33. The lower end ofthe opening 42 is shaped to provide an extended hearing contact with theadjacent outer surfaces of the cylinder 33 and the latter surfaces aremaintained in contact with the block by a set screw 43 threadablysupported in the block at the top of the latter in a position to extendinto the upper end of the opening 42 and engage the cylinder 33. Asshown in Fig. 11, the bottom of the block 41 is slotted or cut away toprovide a clearance opening 44 directly opposite an intake port 45formed in the cylinder 33 at the bottom of the latter. The arrangementis such that the intake port 45 is accessible for connection to a sourceof molten metal supply which will be more fully hereinafter described.

Mounted within the cylinder 33 is a plunger 46 having a reduced part atthe outer end externally threaded for detachable engagement by a head 47which, as shown in Fig. 4, is dimensioned to slidably engage the innersurface of the cylinder 33. The inner end of the head 47 is spaced fromthe shoulder 44 formed on the plunger 56 and a piston 57 slidablysupported within the cess 49 of the bearing by the reduced outer end ofthe latter and rings 45' of sealing material are supported on thereduced outer end of the plunger 46. These rings have a wiping action onthe inner surface of the cylinder 33 during movement of the plunger 46in the cylinder and are clamped in place against the shoulder 44' by thehead 47. As shown in Figures 6-8 inclusive of the drawings, the innerend of the plunger 46 is supported by a bearing block 48 having a recess49 which is open at the top to freely receive the inner end of theplunger 46 and a clamping member 536. The portion of the recess 49 atthe outer end of the block 48 is shaped to form a saddle 51 forsupporting the inner end of the plunger 46, and the clamping member 5%assumes a position in the recess 49 at the inner end of the plunger 46.An annular enlargement 52 is formed on the inner end of the plunger 46and abuts a shoulder 53 formed on the bearing block 48 to preventoutward axial displacement of the plunger 46 relative to the bearingblock 48. Inward axial displacement of the plunger 46 relative to thebearing block 48 is prevented by the clamping member 50 which is securedin the reblock by a stud 53'. Upward displacement of the inner end ofthe plunger 46 relative to the bearing block 48 is prevented by a rib 54formed on the outer face of the clamping member 56 in a position toengage the top of the enlargement 52, as shown in Figures 6 and 8 of thedrawings. The above construction is such that the inner end of theplunger 46 is readily removably secured to the bearing block 48.

The bearing block 48 also serves as a coupling for connecting the innerend of the plunger 46 to a hydraulic motor 55. The hydraulic motor 55comprises a cylinder cylinder 56. As shown in Figure 1 of the drawings,the outer end of the cylinder 56 is secured to a suitable support 58 andthe piston 57 is connected to a rod 59 which projects outwardly throughthe outer end of the cylinder I 56. The outer end of the rod 59 issecured to the bearing block 48 in a manner such that movement of thepiston 57 in the cylinder 56 imparts a corresponding movement to theplunger 46.

As shown in Figure 12 of the drawings, the piston 57 is operated by ahydraulic fluid medium contained in a reservoir 69 and circulated by apump 61. The intake side of the pump 61 is connected to the reservoir 60by a conduit 62 and the discharge side of the pump is connected to acontrol valve 63. The valve 63 is, in turn, connected to opposite endsof the cylinder 56 and to the reservoir 60 in a manner such thatmovement of the valve in opposite directions alternately connectsopposite ends of the cylinder 56 to the pump and reservoir. The valve 63may be and preferably is automatically operated to move the plunger 46back and forth in the cylinder 33 in accordance with a predeterminedtimed cycle of operation. The means for automatically operating thevalve 63 is not shown herein but may be and preferably is the same asthe means disclosed in my copending application Serial No. 382,079.

More particularly, upon completion of a casting in the die 20, the partsof the latter are relatively moved to their open positions and theejection plate 29 is operated to eject the casting from the die cavity24. At the same time, the ejection plate 29 engages the plug 34 andmoves the same inwardly into sealing relationship with the outer end ofthe cylinder 33. The valve 63 then operates to connect the outer end ofthe cylinder 56 to the pressure side of the pump 61 and to connect theinner end of the cylinder 56 to the reservoir 60. Thus the piston 57 ismoved in an inward direction in the cylinder 56 to impart acorresponding inward movement to the plunger 46 in the cylinder 33.Since the outer end of the cylinder 33 is closed by the plug 34, inwardmovement of the plunger 46 produces a vacuum in the cylinder 33 and theresulting suction is communicated to the intake port 45 when the plunger46 assumes its retracted position inwardly beyond the intake port 45.

As will be presently described, this suction draws a quantity of moltencasting material such, for example, as aluminum or alloys of aluminumupwardly through the port 45 into the cylinder 33 at the outer side ofthe plunger 46. Upon completion of this operation, the valve 63 againoperates to reverse the connections aforesaid to the pump 61 andreservoir 60 to move the plunger 46 out- Initial outward movement of theplunger 46 closes the intake port 45 in the cylinder 33 and continuedoutward movement of the plunger 46 forces the molten material into thedie cavity 24 which has previously been closed. In this connection itwill be understood that the ejector plate 29 is moved to its inoperativeposition in timed relation to closing of the die cavity 24, enabling theplug 34 to be moved outwardly relative to the not obstruct the flow ofmolten casting material from the cylinder 33 into the die cavity 24.

The vacuum produced within the cylinder 33 upon retracting movement ofthe plunger 46 is sufficient to draw the amount of molten castingmaterial into the cylinder 33 required to properly fill the die cavity24 and associated The vacuum or the amount of pressure drop produced inthe cylinder 33 may be varied by regulating the rate of retraction ofthe plunger 46 and/ or by providing relief areas in the seating surfaceof either the plug 34 or adjacent end of the cylinder 33 to enable theescape of a limited amount of air into the cylinder 33 as the plunger 46is moved inwardly relative to this cylinder.

In order to produce satisfactory castings on a high volume productionbasis with a minimum loss of shutdown time for servicing, it isessential to not only supply the correct amount of molten castingmaterial to the die cavity 24, but to also maintain this predeterminedsupply uniform over long periods of operation. in accordance with thepresent invention the quantity of molten casting material supplied tothe cylinder 33 is metered with respect to the pressure drop created inthe cylinder 33 upon retracting movement of the plunger 46, and withrespect to the capacity of the die cavity 24 and associated passage orpassages 25. However, this feature alone does not assure satisfactoryoperation for long periods without servicing especially in instanceswhere the molten casting material employed has a physical as well as achemical action on the material through which the metering orifice isformed. Such casting materials attack the Walls of the orifice andincrease the size of the orifice to such an extent that far too great aquantity of molten casting material is supplied to the cylinder 33.

The foregoing is a critical problem in the commercial application of diecasting apparatus of the type disclosed herein and this problem issolved by the structure of the unit to be presently described forconnecting the intake port 45 in the cylinder 33 to a source of supply65 for the molten casting material. In detail, the source of supply 65comprises a container 66 supported in any suitable manner directly belowthe intake port 45 formed in the pressure cylinder 33 and having the topopen to the atmosphere. Positioned between the container 66 and thecylinder 33 is a conducting device 67 for molten casting material housedwithin the container 66. The device 67 has a block 68 elongated in avertical direction and fashioned with a supply passage 69 extendingthere through from one end to the other. The bottom portion of the block68 projects into the container 66 through the open top of the latter andis immersed into the molten casting material. Thus, the atmosphericpressure acting on the top surface of the molten casting material in thecontainer 66 tends to force this material upwardly through the supplypassage 69.

The wall of the block 68 forming the top of the passage 69 is taperedoutwardly to provide an annular seat 70 for the lower end of a plug 71which is correspondingly tapered to provide a fluid tight joint with theblock 68, and which has a vertically extending metering passage 72registering with the passage 69. The upper end of the plug 71 projectsinto a recess 73 formed in the cylinder 33 around the intake port 45,and the passage 72 in the plug also registers with the intake port 45.As shown in Figure 16 the upper end of the plug 71 is fashioned with anannular seat 73 surrounding the corresponding end cally shaped and theseat 73 is rounded in cross section to have a continuous line contactwith the seat 74. Thus, a fluid tight joint is provided between theseats with a minimum area of contact of the seating surfaces. This thatthe plug is not only removably supported on the block 68 but, inaddition, is reversible. Hence, should one of the seats 73 becomedefective, the plug 71 may merely be reversed and, should the plugbecome otherwise defective, it may be readily replaced. Also, the plug71 may be quickly interchanged with plugs having metering passages 72 ofdiiferent cross sectional areas.

It follows from the above that the amount of molten material admitted tothe cylinder 33 through the intake as uniform operation of the diecasting equipment for long periods of use without servicing, the plug 71is formed of a sintered compound such as tungsten carbide,

cross sectional area of the metering passage 72 uniform over longperiods of use.

In operation, the molten material drawn into the cylinder 33 through theintake port 45 impinges on the wall directly opposite the port 45 andeventually causes severe corrosion of the metal. In order to overcomethis objection, a plug 75 is removably secured to the wall of thecylinder 33 directly opposite the intake port 45 by the set screw 43.The plug 75 may be formed of the same material as the plug 71 and, inany case, is readily replaceable.

In the present instance, the block 68 together with the plug 71 issupported for movement toward and away respectively extending upwardlyalong opposite sides of the cylinder 33 and, respectively, threadablyengageable with the lower ends of rods 78. The rods 78 slidably engageopposite sides of the block 41 and the upper ends '7 of the rods arereduced to provide annular shoulders 79. The reduced upper ends of therods extend through openings formed in a cross head 80 at opposite endsof the latter, and bushings 81 are respectively supported by the crosshead 83 within the openings to slidably engage the rods 78.

The cross head 80 is normally urged in a downward direction toward stops82, seated on the shoulders 79, by coil springs 83 respectivelysurrounding the upper ends of the rods 78. The lower ends of the coilsprings 83 engage the cross head 80 and the upper ends of the springs 83engage adjusting nuts 84 secured to the upper end of the rods 78. Thecentral portion of the cross head 80 between the two rods 78 isconnected to the lower end of a piston rod 85 having the upper endconnected to a piston 86 which is slidably supported within a verticallyextending hydraulic cylinder 87. Any suitable valve controlled means(not shown) may be provided for alternately connecting opposite ends ofthe cylinder 87 to a reservoir and a source of hydraulic fluid underpressure. The arrangement is such that movement of the cross head 80 ina downward direction by the piston 86, lowers the yoke 76 suflicientlyto disengage the plug '71 from the cylinder 33. On the other hand,movement of the cross head 80 upwardly by the piston 86, raises the yoke76 and engages the plug 71 with the cylinder 33. In this connectionattention is called to the fact that upward movement of the plug 71 intoengagement with the cylinder 33 is effected through the coil springs 83with the result that said springs absorb the shock of engagement of theplug 71 with the cylinder 33 and prevent damage to the seating surfaceson the plug and cylinder.

In order to avoid overheating the cylinder 33 and plunger 46 by themolten metal during the ejecting operation, provision is made herein forcooling the aforesaid parts. As shown in Figures 4, 5, 9 and of thedrawings, the outer end of the cylinder 33 is fashioned to provide aseries of passages 88. The passages 38 extend in the general directionof length of the cylinder 33, but are inclined with respect to thecylinder axis to such an extent that the ends of adjacent passagescommunicate with one another and provide in effect a single circuitouspassage. Water or some other cooling medium is circulated through thepassages and for accomplishing this result intake and outlet conduits 89and 90 are respectively connected to opposite ends of the circuitouspassage formed by the passages 83. In addition to the above coolingarrangement, the cylinder 33 has diametrically opposed bores 91extending axially outwardly from the inner end of the cylinder andconnected to outlet conduits 92, as shown in Figure 4 of the drawings.Extending axially into each of the bores 91 from the inner end of thecylinder 33 is a tube 93 having a diameter substantially less than thediameter of the bores 91 to provide a jacket for a cooling medium withinthe bores 91. The inner ends of the tubes 93 are respectively connectedto intake conduits 94 which in turn communicate with a source of coolingmedium supply, not shown herein. Thus, it will be seen that the cylinder33 is effectively cooled and is maintained at a more or less uniformtemperature throughout the operation of the apparatus.

As shown in Figures 2, 4, 6 and of the drawings the plunger 46 has abore 95 which extends axially of the plunger from the inner end of thelatter and is divided into two communicating passages 96 by a partition97. Referring now to Figure 2 of the drawings, it will be noted that onepassage 96 communicates with an intake couduit 98 for cooling mediumunder pressure, and the other passage 96 communicates with an outletconduit 99 for the cooling medium. Consequently, the cooling medium iscirculated axially of the plunger 46 and the latter is also maintainedat a substantially uniform temperature during the casting operation.

Provision is also made herein for lubricating the inner surface of thecylinder 33 during operation of the plunger 46. For accomplishing thisresult, the plunger 46 is formed with an axially extending lubricantpassage 100. The inner end of the passage 1% is connected to a source oflubricant supply by a conduit 102 and the outer end of the passagecommunicates with the interior of the cylinder 33 at the inner side ofthe head 47 on the plunger 41% through ports N3.

In the present instance, the lubricant supply conduit 132 is connectedto a lubricant supply cylinder 104 through a control valve 105 and aregulating valve 106 by a conduit 107, as shown in Figure 14 of thedrawings. The cylinder 164 contains lubricant under pressure so thatopening of the valve 105 causes lubricant to flow into the cylinder 33through the passage in the plunger 46 at a rate depending upon theadjustment of the valve W6. The valve Hi5 is operated to supplylubricant to the cylinder 33 each time the die 20 is closed and isactuated by a roller 1% mounted on the slide 27. If desired, thelubricant supply tube 37 for the closure plug 34 may also be connectedto the conduit 107 so that a supply of lubricant is introduced into thebore in the die part 22 each time the die is closed.

What I claim as my invention is:

l. in a pressure casting apparatus, a mold cavity, a pressure cylinderhaving a discharge opening for molten casting material communicatingwith the cavity and having an inta 1e opening for molten castingmaterial spaced inwardly from said discharge opening axially of saidcylinder, a plunger movable in said pressure cylinder in an outwarddirection outwardly beyond said intake opening to inject molten castingmaterial into said cavity and movable in an inward direction to aretracted position inwardly beyond the intake opening, means for closingsaid discharge opening upon initial inward movement of said plungertoward its retracted position to provide a vacuum in said pressurecylinder produced solely by the inward movement of said plunger andsuflicient to draw molten casting material into said cylinder throughsaid intake opening when the latter is uncovered by movement of saidplunger to its retracted position, means for admitting molten castingmaterial to said pressure cylinder including a part having a passagecommunicating with said intake opening and of a cross-sectional areapredetermined to admit a metered amount of molten casting material tosaid pressure cylinder in response to the vacuum produced in saidcylinder by said plunger, said part being formed of a materialcharacterized in that it withstands the temperature of the moltencasting material without deterioration and is not affected by thephysical and chemical action of the molten material flowing through thepassage in said part.

2. The structure defined in claim 1 wherein said part is formed of amaterial selected from the group consisting of tungsten carbide,titanium carbide and zirconium boride and a binder selected from thegroup consisting of cobalt and platinum.

3. In a pressure casting apparatus, a mold cavity, a pressure cylinderhaving a discharge opening for molten casting material communicatingwith the cavity and having an intake opening for molten casting materialspaced inwardly from said discharge opening axially of said cylinder, aplunger movable in said pressure cylinder in an outward directionoutwardly beyond said intake opening to inject molten casting materialinto said cavity and movable in an inward direction to a retractedposition inwardly beyond the intake opening, means for closing saiddischarge opening upon initial inward movement of said plunger towardits retracted position to provide a vacuum in said pressure cylinderproduced solely by the inward movement of said plunger and sufficient todraw molten casting material into said cylinder through said intakeopening when the latter is uncovered by movement of said plunger to itsretracted position, a container for a supply of molten casting materialsupported below said pressure cylinder, a member projecting downwardlyinto said container below the level of the molten casting material insaid container and having a vertically extending passage communicatingat the lower end with level of the molten casting material andcommunicating at the upper end with said ing of tungsten carbide,titanium boride and a binder selected cobalt and platinum.

4. The structure defined in claim 3 comprising an ancarbide andzirconium from the group consisting of an intake opening for moltenmaterial, ducing molten material through the intake opening sage formolten material means for introinto the pressure chamber including apart having a pasof a cross-sectional area preship with respect to 7.The structure the pressure chamber. defined in claim 6 wherein the partis reversible end for end and 1s removably mounted on the support ineither position thereof.

8. In pressure casting apparatus, a mold cavity, a prescross-sectionalarea predetermined to meter the flow of casting material admitted tosaid pressure chamber, said part being formed of a materialcharacterized in that it withstands the temperature of the moltencasting material and is not affected by physical and chemical action ofthe casting material whereby the predetermined crosssectional area ofsaid passage is maintained for long periods of use, and means forexpelling the casting material admitted to said chamber from saiddischarge opening, said chamber having an annular seating surfacesurrounding said intake opening at the outer side of the latter, andsaid part having an annular seating surface engageable 10 with theseating surface on said chamber, said part be ing formed of a sinteredcarbide material, and said seating surfaces having cross-sectionalcontours predetermined to provide a continuous line contact therebetweenand thereby reduce heat transfer between said part and chamber to aminimum.

9. In pressure casting apparatus, a .mold cavity, a pressure chamberhaving a discharge opening communicating with said mold cavity andhaving an intake opening, means for introducing molten casting materialinto said pressure chamber through said intake opening including a parthaving a passage for molten casting material of a cross-sectional areapredetermined to meter the flow of casting material admitted to saidpressure chamber, said part being formed of a material characterized inthat it withstands the temperature of the molten casting material and isnot affected by physical and chemical action of the casting materialwhereby the predetermined cross-sectional area of said passage ismaintained for long periods of use, and means for expelling the castingmaterial admitted to said chamber from said discharge opening, saidchamber having an annular seating surface surrounding said intakeopening at the outer side of the latter, and said part having an annularseating surface engageable with the seating surface on said chamber,said seating surfaces having cross-sectional contours predetermined toprovide a continuous line contact therebetween and thereby reduce heattransfer between said part and said chamber to a minimum.

10. In pressure casting apparatus, a mold cavity, means for supplyingmolten casting material to said cavity including a pressure chamberhaving a discharge opening, said chamber also having an intake opening,means for introducing molten casting material into said pressure chamberthrough said intake opening including a part having a passage for moltencasting material of a crosssectional area predetermined to meter theflow of casting material admitted to said pressure chamber, means forexpelling the casting material admitted to said chamber from saiddischarge opening, said chamber having an annular seating surfacesurrounding said intake opening at the outer side of the latter, andsaid part having an annular seating surface engageable with the seatingsurface on said chamber, said seating surfaces having cross-sectionalcontours predetermined to provide a continuous line contact therebetweenand thereby reduce heat transfer between said part and said chamber to aminimum.

11. In a pressure casting apparatus, a mold cavity, means for deliveringmolten casting material to said mold cavity incuding a pressure cylinderhaving a discharge opening, a plunger supported in said cylinder foraxial sliding movement in one direction toward said discharge opening toexpel casting material in said cylinder from said discharge opening andin the opposite direction away from said discharge opening to aretracted position, said cylinder having an intake port between saiddischarge opening and said plunger in the retracted position of thelatter, means for admitting molten casting material to said cylinderincluding a part having a supply passage communicating with said intakeport and with a supply of molten casting material, and means for closingsaid discharge opening during movement of said plunger in said oppositedirection to its retracted position to provide a vacuum in said cylinderat the side of said plunger toward said discharge opening producedsolely by the movement of said plunger in said opposite direction andsuflicient to draw molten casting material through said supply passageinto said cylinder through said intake port, said passage being of across-sectional area predetermined to admit a metered amount of moltencasting material to said cylinder in response therein by said plunger,and said part being formed of a material characterized in that itwithstands the temperature of the molten casting '11 material withoutdeterioration and is not a'fiected by the physical and chemical actionof the molten material flowing through the passage in said part.

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